U.S. patent application number 15/814399 was filed with the patent office on 2018-06-14 for hemispherical resonance micromechanical gyroscope and processing method thereof.
This patent application is currently assigned to SUZHOU WENZHIXIN MICRO SYSTEM TECHNOLOGY CO., LTD. The applicant listed for this patent is SUZHOU WENZHIXIN MICRO SYSTEM TECHNOLOGY CO., LTD. Invention is credited to Shuwen Guo.
Application Number | 20180164098 15/814399 |
Document ID | / |
Family ID | 62495524 |
Filed Date | 2018-06-14 |
United States Patent
Application |
20180164098 |
Kind Code |
A1 |
Guo; Shuwen |
June 14, 2018 |
HEMISPHERICAL RESONANCE MICROMECHANICAL GYROSCOPE AND PROCESSING
METHOD THEREOF
Abstract
The present invention relates to a micromachined hemispherical
resonance gyroscope, which includes a resonant layer, wherein the
resonant layer comprises a hemispherical shell whose top point of
the hemispherical shell is its anchor point; several silicon
hemispherical electrodes are ananged around the hemispherical
shell, the silicon hemispherical electrodes include driving
electrodes, equilibrium electrodes, shielded electrodes and signal
detection electrodes or quadrature correction electrodes, the
hemispherical shell and the several silicon spherical electrodes
which sunound the hemispherical shell constitute several
capacitors. The hemispherical resonance micromechanical gyroscope
utilizes a processing method on the basis of silicon
micromachining, which leads to small size and low production cost,
as well as batch production capacity, meanwhile its sensitivity is
independent of amplitude and its driving voltage could be very low,
as a result its output noise could be significantly reduced, and
its accuracy is better than the gyroscope products in the prior
art.
Inventors: |
Guo; Shuwen; (JIANGSU,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUZHOU WENZHIXIN MICRO SYSTEM TECHNOLOGY CO., LTD |
JIANGSU |
|
CN |
|
|
Assignee: |
SUZHOU WENZHIXIN MICRO SYSTEM
TECHNOLOGY CO., LTD
JIANGSU
CN
|
Family ID: |
62495524 |
Appl. No.: |
15/814399 |
Filed: |
November 16, 2017 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
14408177 |
Oct 21, 2015 |
|
|
|
PCT/CN2012/080825 |
Aug 31, 2012 |
|
|
|
15814399 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01C 25/005 20130101;
G01C 19/5691 20130101; G01P 15/02 20130101; G01C 19/5719
20130101 |
International
Class: |
G01C 19/5691 20060101
G01C019/5691; G01C 19/5719 20060101 G01C019/5719; G01C 25/00
20060101 G01C025/00; G01P 15/02 20060101 G01P015/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 15, 2012 |
CN |
201210182174.5 |
Jul 15, 2012 |
CN |
201210231285.0 |
Claims
1. A hemispherical resonance micromechanical gyroscope, comprising
a resonant layer, wherein the resonant layer comprises: a
hemispherical shell being made of in-situ doped polysilicon,
silicon oxide, silicon nitride, or diamond; and several silicon
spherical electrodes being arranged around the hemispherical shell,
the silicon spherical electrodes include driving electrodes,
shielded electrodes and equilibrium electrodes, signal detection
electrodes or quadrature correction electrodes, wherein the
shielded electrodes converge at a point and the converging point is
an anchor point of the hemispherical shell, the mechanical support
and electrical connection of the shielded electrodes and the
hemispherical shell are accomplished through the anchor point, the
hemispherical shell and the several silicon spherical electrodes
which surround the hemispherical shell constitute several
capacitors, wherein the silicon hemispherical electrodes is formed
by etching deep grooves on the silicon wafer by means of
lithography and DRIE dry etch with a V-shaped groove lithography
board being utilized during etching to make the width of the deep
grooves be proportional to the thickness of the silicon wafer, such
that the window width of the deep grooves close to the anchor point
is relatively narrow, and the window width of the deep grooves
close to the edge of the hemispherical shell is relatively
wide.
2. The hemispherical resonance micromechanical gyroscope according
to claim 1, wherein the number of the silicon spherical electrodes
is 20 or 24, including 4 or 8 shielded electrodes therein, and the
shielded electrodes are symmetrically distributed along the
circumferential direction of the hemispherical shell.
3. The hemispherical resonance micromechanical gyroscope according
to claim 2, wherein the spherical electrodes include 8 shielded
electrodes, and the shielded electrodes separating the driving
electrodes and the equilibrium electrodes from the signal detection
electrodes.
4. The hemispherical resonance micromechanical gyroscope according
to claim 1, wherein the radius of the hemispherical shell is
600-5000 .mu.m.
5. The hemispherical resonance micromechanical gyroscope according
to claim 4, wherein the radius of the hemispherical shell is
1200-1800 .mu.m.
6. The hemispherical resonance micromechanical gyroscope according
to claim 1, wherein the thickness of the hemispherical shell is
0.5-10 .mu.m.
7. The hemispherical resonance micromechanical gyroscope according
to claim 6, wherein the thickness of the hemispherical shell is
2.0-5 .mu.m.
8. The hemispherical resonance micromechanical gyroscope according
to claim 1, wherein the operating resonance mode of the
hemispherical shell having at least four antinodes, and the
resonant frequency is 2.0-150 kHz.
9. The hemispherical resonance micromechanical gyroscope according
to claim 8, wherein the operating resonance mode of the
hemispherical shell having at least four antinodes, and the
resonant frequency is 13-20 kHz.
10. The hemispherical resonance micromechanical gyroscope according
to claim 1, wherein one side of the resonant layer which is close
to the hemispherical shell is bound with a first capping layer, and
the other side of the resonant layer which is close to the silicon
spherical electrodes is bound with a second capping layer; wherein
the first capping layer is a glass plate or a silicon plate grown
silicon oxide, and the second capping layer is made of glass
material containing through-holes or silicon material containing
through-holes, the glass material containing through-holes or
silicon material containing through-holes guides the silicon
spherical electrodes to the surface of the hemispherical resonance
micromechanical gyroscope.
11. A processing method for the hemispherical resonance
micromechanical gyroscope according to claim 1, comprising
following steps: (1) isotropic etching a hemispherical pit on one
side of a silicon wafer; (2) growing a silicon dioxide layer on the
inner surface of the hemispherical pit by thermal oxidation in
order to form a thermal oxide layer, and forming a hole on the
central position of the thermal oxide layer which though the
thermal oxide layer, then depositing a hemispherical shell layer on
the outside of the thermal oxide layer and the side wall and the
bottom surface of the hole, wherein the hemispherical shell layer
is an in-situ doped polysilicon layer, a silicon oxide layer, a
silicon nitride layer, or a diamond film, the polysilicon layer is
connected to the silicon wafer though the hole and the polysilicon,
silicon oxide, silicon nitride, or diamond depositing in the hole
foul's the anchor point; (3) removing the thermal oxide layer and
the hemispherical shell layer outside the inner surface of the
hemispherical pit by using mechanical polishing method; (4) etching
deep grooves on the silicon wafer by means of lithography and DRIE
dry etch on the other side of the silicon wafer to form the silicon
spherical electrodes arranged around the hemispherical shell layer
by utilizing a V-shaped groove lithography board during etching to
make the width of the deep grooves be proportional to the thickness
of the silicon wafer, wherein the thermal oxide layer is used as an
etching stop layer, and etching the thermal oxide layer, forming
the hemispherical shell by the hemispherical shell layer hung at
the anchor point, and the hemispherical shell and the several
silicon spherical electrodes which surround the hemispherical shell
constitute several capacitors; and (5) depositing metal on the
surface of the silicon wafer and performing lithography in order to
complete metallization, finally forming the resonant layer by the
process.
12. The processing method for the hemispherical resonance
micromechanical gyroscope according to claim 11, wherein the
hemispherical pit is etched using isotropic etching method, and the
isotropic etching method includes a dry etching method and a wet
etching method.
13. The processing method for the hemispherical resonance
micromechanical gyroscope according to claim 11, wherein, in step
(4), the thermal oxide layer is etched using gaseous hydrofluoric
acid.
14. The processing method for the hemispherical resonance
micromechanical gyroscope according to claim 11, wherein the
thickness of the thermal oxide layer is 1-2 .mu.m.
15. The processing method for the hemispherical resonance
micromechanical gyroscope according to claim 11, wherein after the
thermal oxide layer and the hemispherical shell layer outside the
inner surface of the hemispherical pit are removed in step (3), the
process further comprises a bonding step to bond a first capping
layer to the one side close to the hemispherical shell of the
silicon wafer.
16. The processing method for the hemispherical resonance
micromechanical gyroscope according to claim 11, further comprising
a step of bonding a second capping layer to the other side close to
the silicon spherical electrodes of the silicon wafer, wherein the
second capping layer is made of glass material, the step comprises:
opening shallow grooves on the surface of the second capping layer
which is bound to the resonant layer using anodic silicon
oxide-glass bonding method; and depositing a getter film layer in
the shallow grooves; and bonding the second capping layer to the
other side close to the silicon spherical electrodes of the silicon
wafer.
17. The processing method for the hemispherical resonance
micromechanical gyroscope according to claim 11, further comprising
a step of bonding a second capping layer to the other side close to
the silicon spherical electrodes of the silicon wafer using
silicon-silicon direct bonding method, wherein the second capping
layer is made of silicon material.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part application of
and claims the priority benefit of a prior U.S. patent application
Ser. No. 14/408,177, filed on Oct. 21, 2015. The prior application
Ser. No. 14/4 08,177 is a 371 of international application of PCT
application serial no. PCT/CN2012/080825, filed on Aug. 31, 2012,
which claims the priority benefit of China application no.
201210231285.0, filed on Jul. 15, 2012, and China application no.
201210182174.5, filed on Jun. 15, 2012. The entirety of each of the
above-mentioned patent applications is hereby incorporated by
reference herein and made a part of this specification.
BACKGROUND
1. Field of the Invention
[0002] The present invention relates to a hemispherical resonance
micromechanical gyroscope, as well as the processing method on the
basis of silicon micromachining used therein.
2. Description of Related Art
[0003] A silicon micromechanical gyroscope has a wide range of
application prospects in the field of inertial measurement due to
its advantages such as small size, low cost, low power consumption,
impact resistance and high reliability. However, accuracy of a MEMS
gyroscope product is much lower than a FOG or a laser gyroscope,
mainly because the accuracy depends on the size of its amplitude
for most of the MEMS resonance gyroscopes, and the noise signal
increases along with the increase of the amplitude, which restricts
improvement of the SNR. Due to the low accuracy, its application
field is greatly restricted.
[0004] A traditional hemispherical resonance gyroscope is made of
quartz, and its principle is based on cup body vibration theory
proposed by Professor Bryan of the university of Cambridge one
hundred years ago. The theory indicates that during a hemispherical
cup body rotates around the centreline of the cup, its four
antinodes vibration pattern will deflect. By detecting the phase
changes of the deflection vibration pattern, an angular
acceleration signal could be acquired. The hemispherical resonance
gyroscope has a very accurate scale factor and a satisfactory
random drift and bias stability, and the gain and the scale factor
of the gyroscope are independent of its material, which are only
the functions of the stress wave oscillation mode on the thin
shell. The gyroscope is not sensitive to the external environment
(acceleration, vibration, temperature, etc.), and even the
temperature compensation is not required by the gyroscope,
therefore the hemispherical resonance gyroscope is recognized in
the inertial technology field as one of the best gyroscope products
with high performance at present, which has an accuracy higher than
the FOG or the laser gyroscope, as well as additional advantages
such as high resolution, wide measuring range, resistance to
overload, anti-radiation, anti-interference, etc.
[0005] However, the traditional hemispherical resonance gyroscope
is made of fused quartz, which makes it difficult to process and
highly cost. Its price is up to several hundred thousands to a
million dollars, as a result it can't be widely used. In addition,
its size is also too large, and the diameter of the hemispherical
resonance gyroscope with minimum size is still up to 20 mm
currently. Therefore, the development of a new generation of
hemispherical resonance gyroscope with miniature size and low cost
naturally becomes the target in inertial technology field.
SUMMARY
[0006] It's an object of the present invention to provide a new
type of MEMS hemispherical resonance gyroscope on the basis of
phase detection principle with high accuracy, small size and low
cost, as well as the processing method on the basis of silicon
micromachining used therein.
[0007] The object of the present invention has been achieved by the
following technical means.
[0008] A hemispherical resonance micromechanical gyroscope, which
comprises a resonant layer comprising a hemispherical shell and
several silicon hemispherical electrodes being arranged around the
hemispherical shell, the silicon spherical electrodes include
driving electrodes, equilibrium electrodes, shielded electrodes and
equilibrium electrodes, signal detection electrodes or quadrature
correction electrodes, the shielded electrodes separate the driving
electrodes and the equilibrium electrodes from the signal detection
electrodes, and the shielded electrodes converge at a point and the
converging point is anchor point of the hemispherical shell, the
mechanical support and electrical connection of the shielded
electrodes and the hemispherical shell are accomplished through the
anchor point, the hemispherical shell and the several silicon
spherical electrodes which surround the hemispherical shell
constitute several capacitors, and the hemispherical shell is made
of in-situ doped polysilicon, silicon oxide, silicon nitride, or
diamond.
[0009] In some embodiments, the number of the silicon hemispherical
electrodes is 20 or 24, including 4 or 8 shielded electrodes
therein, and the shielded electrodes are averagely and
symmetrically distributed along the circumferential direction of
the hemispherical shell.
[0010] In some embodiments, the radius of the hemispherical shell
is 600-5000 .mu.m, which is typically 1200-1800 .mu.m; and the
thickness of the hemispherical shell is 0.5-10 .mu.m, which is
typically 1.5-2.0 .mu.m.
[0011] In some embodiments, the operating resonance mode of the
hemispherical shell, i.e. the minimum resonance mode is four
antinodes mode, and the resonant frequency is 2.0-15.0 kHz, which
is typically 13-20 kHz.
[0012] In some embodiments, one side of the resonant layer which is
close to the hemispherical shell is bound with a first capping
layer, and the other side of the resonant layer which is close to
the silicon hemispherical electrodes is bound with a second capping
layer; wherein the first capping layer is a glass plate or a
silicon plate with a silicon oxide layer, and the second capping
layer is made of glass material containing through-holes or silicon
material containing through-holes, the glass material containing
through-holes or silicon material containing through-holes guides
the silicon hemispherical electrodes to the surface of the
hemispherical resonance micromechanical gyroscope.
[0013] A processing method for the hemispherical resonance
micromechanical gyroscope mentioned above, which comprises
following steps:
[0014] (1) isotropic etching a hemispherical pit on one side of a
silicon wafer;
[0015] (2) growing a layer of thermal oxide layer with a thickness
of about 1-2 .mu.m grow on the inner surface of the hemispherical
pit, and etching the central position (anchor position) of the
thermal oxide layer to form a hole which is preferably a round hole
by using lithography and etching on bottom of the pit, then
depositing a layer of LPCVD polysilicon layer on the outside of the
thermal oxide layer and the side wall and the bottom surface of the
hole, i.e. the hemispherical shell layer, the hole cuts though the
thermal oxide layer and extends to the silicon wafer, thus the
polysilicon layer is connected to the silicon wafer though the
round hole and depositing hemispherical shell layer on outer
surface of the thermal oxide layer, wherein the hemispherical shell
layer is an in-situ doped polysilicon layer, a silicon oxide layer,
a silicon nitride layer, or a diamond film;
[0016] (3) removing the thermal oxide layer and the hemispherical
shell layer outside the inner surface of the hemispherical pit;
[0017] (4) etching to form silicon hemispherical electrodes
arranged around the hemispherical shell layer on the other side of
the silicon wafer by deep reactive ion etching (DRIE), wherein the
thermal oxide layer being used as an etching stop layer, and
removing the theimal oxide layer after DRIE, the hemispherical
shell formed by the hemispherical shell layer being hung at an
anchor point, and the hemispherical shell and the several silicon
spherical electrodes surrounding the hemispherical shell constitute
several capacitors;
[0018] (5) depositing and patterning a metal layer on the surface
of the silicon wafer to complete metallization, finally forming the
resonant layer by the process.
[0019] In some embodiments, in the step (4), etching the deep
grooves on the silicon wafer by means of photolithography and DRIE
to form the silicon hemispherical electrodes, wherein a V-shaped
groove photolithography board is utilized during etching, and the
width of the deep grooves is proportional to the thickness of the
silicon wafer.
[0020] In some embodiments, in step (1), the hemispherical pit is
etched using by isotropic etching, and the isotropic etching
includes dry etching and wet etching.
[0021] In some embodiments, in step (3), the thermal oxide layer
and the polysilicon layer is removed by mechanical polishing.
[0022] In some embodiments, in the step (4), the thermal oxide
layer is etched by gaseous hydrofluoric acid.
[0023] In some embodiments, the thickness of the thermal oxide
layer is 1-2 .mu.m.
[0024] In some embodiments, in the step (3), after the thermal
oxide layer and the hemispherical shell layer are removed, the
first capping layer is bound to the side close to the hemispherical
shell of the silicon wafer.
[0025] In some embodiments, in the step (5), the second capping
layer is bound to the side close to the silicon hemispherical
electrodes of the silicon wafer; the bonding method comprises
opening a shallow grooves on the surface of the second capping
layer which is bound to the resonant layer using anodic silicon
oxide-glass bonding method when the second capping layer is made of
glass material, and depositing a getter film layer in the shallow
grooves, then performing the bonding; or utilizing silicon-silicon
direct bonding method when the second capping layer is made of
silicon material.
[0026] Due to the technical solution mentioned above, the present
invention has following advantages compared with prior art:
[0027] The sensitivity of the silicon hemispherical resonance
micromechanical gyroscope of the present invention doesn't depend
on its amplitude, and it has a lower driving voltage, therefore its
output noise could be significantly reduced, and its accuracy could
be raised than the gyroscope products in the prior art;
[0028] The hemispherical resonance micromechanical gyroscope of the
present invention utilizes processing method on the basis of
silicon micromachining, which leads to small size and low
production cost, as well as batch production capacity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a distribution diagram of the silicon
hemispherical electrodes of the hemispherical resonance
micromechanical gyroscope of the present invention;
[0030] FIG. 2 is a diagram illustrating the shielded electrodes
supporting the hemispherical shell of the hemispherical resonance
micromechanical gyroscope of the present invention;
[0031] FIG. 3 is a flow chart illustrating processing method of the
hemispherical resonance micromechanical gyroscope of the present
invention;
[0032] FIG. 4 is a window diagram illustrating the silicon
hemispherical electrodes being formed by deep grooves etching of
the hemispherical resonance micromechanical gyroscope of the
present invention;
[0033] FIG. 5 is a cross-sectional diagram of the silicon wafer of
the hemispherical resonance micromechanical gyroscope of the
present invention, wherein the hemispherical shell is not
shown;
[0034] FIG. 6 is a diagram of the hemispherical resonance
micromechanical gyroscope of the present invention before the
second capping layer being bound to it;
[0035] FIG. 7 is a working principle diagram of the hemispherical
resonance micromechanical gyroscope of the present invention;
[0036] FIG. 8 is a four antinodes mode analysis diagram of the
hemispherical resonance micromechanical gyroscope of the present
invention;
[0037] FIG. 9 is a three antinodes mode analysis diagram of the
hemispherical resonance micromechanical gyroscope of the present
invention;
[0038] FIG. 10 is a five antinodes mode analysis diagram of the
hemispherical resonance micromechanical gyroscope of the present
invention;
[0039] FIG. 11 is a pendulum resonance mode analysis diagram of the
hemispherical resonance micromechanical gyroscope of the present
invention;
[0040] FIG. 12 is a perspective view of the second capping layer
illustrating shallow grooves with a deposited getter film layer of
the hemispherical resonance micromechanical gyroscope of the
present invention;
[0041] FIG. 13 is a distribution diagram of the silicon
hemispherical electrodes of another embodiment of the present
invention, wherein the hemispherical shell is not shown;
[0042] FIG. 14 illustrates the hemispherical shell and the shielded
electrodes of another embodiment of the present invention;
[0043] FIG. 15 is a partial sections of the resonant layer of
another embodiment of the present invention.
[0044] In FIGS mentioned above:
[0045] 1 resonant layer; 2 hemispherical shell; 2a anchor point; 20
polysilicon layer; 3 deep grooves; 4 driving electrodes; 5
equilibrium (or forcer) electrodes; 6 signal detection electrodes;
7 shielded electrodes; 8 the nial oxide layer; 9. first capping
layer; 10 hemispherical pit; 10a hole; 11 second capping layer; 12
shallow grooves; 13 getter film layer; 14 quadrature correction
electrodes.
DESCRIPTION OF THE EMBODIMENTS
[0046] Now, embodiments of the present invention will be described
in detail by reference to the accompanying drawings.
[0047] A hemispherical resonance micromechanical gyroscope, which
comprises a resonant layer 1, a first capping layer 9 and a second
capping layer being bound on both sides of the resonant layer 1, as
shown in FIG. 1 and FIG. 2.
[0048] The resonant layer 1 comprises a hemispherical shell 2 and
several silicon spherical electrodes arranged around the
hemispherical shell 2. The hemispherical shell 2 could be made of
in-situ doped polysilicon, silicon oxide, silicon nitride or
diamond. In the present embodiment, it's made of polysilicon. The
hemispherical shell 2 has a concave inner surface and an outer
surface opposite to the inner surface, and top point of the
hemispherical shell being its anchor point. The silicon spherical
electrodes are formed by etching several deep grooves 3 on a
silicon wafer and made of a high-doped monocrystalline silicon
material. The number of the silicon spherical electrodes is 20 or
24, including driving electrodes 4, equilibrium electrodes (or
forcer) 5, signal detection electrodes 6 and shielded electrodes 7.
In the present embodiment, there are eight shielded electrodes 7
which are symmetrically distributed along the circumferential
direction of the hemispherical shell 2, and the shielded electrodes
7 separate the driving electrodes 4 and the equilibrium electrodes
5 from the signal detection electrodes 6. Therefore, coupling
coefficient of the driving electrodes 4 and the signal detection
electrodes 6 is reduced, resulting in a reduction of quadrature
error and noise. The shielded electrodes 7 converge at a point and
the converging point is an anchor point of the hemispherical shell
2, so that the shielded electrodes 7 could serve to support the
hemispherical shell 2. The mechanical support and electrical
connection of the shielded electrodes 7 and the hemispherical shell
2 are accomplished through the anchor point. The hemispherical
shell 2 and several silicon spherical electrodes surrounding the
hemispherical shell 2 constitute several capacitors. The radius of
the hemispherical shell 2 is 1200-1800 .mu.m, which is typically
1300 and the thickness of the hemispherical shell 2 is 0.5-2.5
.mu.m, which is typically 2.0 .mu.m.
[0049] The first capping layer 9 is a glass plate or a silicon
plate with silicon oxide, and the second capping layer 11 is made
of glass material containing through-holes or silicon material
containing through-holes, the glass material containing
through-holes or silicon material containing through-holes guides
the silicon hemispherical electrodes to the surface of the
hemispherical resonance micromechanical gyroscope.
[0050] As shown in FIG. 3, the hemispherical resonance
micromechanical gyroscope mentioned above utilizes a processing
method on the basis of silicon micromachining. The processing
method includes following steps.
[0051] (1) A hemispherical pit 10 with a radius of 1200-1800 .mu.m
on the (111) surface of the silicon wafer is etched by isotropic
etching (including dry etching and wet etching), and the etched
surface is as smooth as a mirror.
[0052] (2) A layer of thermal oxide layer 8 with a thickness of
about 1-2 .mu.m is grown on the inner surface of the hemispherical
pit 10, and the central position (anchor position) of the theimal
oxide layer 8 is etched to form a hole 10a which is preferably a
round hole by using lithography and etching on bottom of the pit
10. A layer of LPCVD in-situ doped polysilicon layer 20 is
deposited on the outside of the thermal oxide layer 8 and the side
wall and the bottom surface of the hole 10a, i.e. the hemispherical
shell layer. The hole 10a cuts though the thermal oxide layer 8 and
is communicated with the silicon wafer, thus the polysilicon layer
20 is connected to the silicon wafer though the round hole 10a, and
the polysilicon depositing in the round hole 10a forms the anchor
point.
[0053] (3) The thermal oxide layer 8 and the polysilicon layer
outside the inner surface of the hemispherical pit 10 is removed by
mechanical polishing. Therefore, the thermal oxide layer 8 and the
polysilicon layer are only retained on the inner surface of the
hemispherical pit 10. A silicon-glass bonding to one side of the
silicon wafer close to the polysilicon layer with a glass plate is
made by using anodic oxidation method, or is directly bound with a
silicon plate grown with a silicon oxide layer, i.e. bound with the
first capping layer 9.
[0054] (4) Etching deep grooves 3 on the other side of the silicon
wafer by lithography and DRIE dry etch to form the silicon
hemispherical electrodes surrounding the hemispherical shell 2, and
sacrifice the thermal oxide layer to form the resonant layer 1. The
thermal oxide layer 8 is used as an etching stop layer. As shown in
FIG. 4 and FIG. 5, a V-shaped groove lithography board is utilized
during etch, and the width of the deep grooves 3 is proportional to
the thickness of the silicon wafer. As the section thickness of the
silicon wafer is uneven due to existence of the hemispherical pit
10, the thermal oxide layer 8 growing thereof is also spherical.
During etching of the deep grooves 3 from top to bottom (wherein
"top" and "bottom" means the top and bottom direction shown in FIG.
4), the etch rate is proportional to a window width of the deep
grooves 3, and when the thinner positions of the silicon wafer has
been penetrated, the etching to the thicker positions of the
silicon wafer has not been finished. In order to prevent this
phenomenon, the V-shaped groove lithography board mentioned above
is utilized, which makes the window width of the deep grooves 3
close to the anchor point relatively narrow, and the window width
of the deep grooves 3 close to the edge of the hemispherical shell
2 relatively wide. Therefore, the deep grooves 3 appearing on the
silicon wafer are V-shape in the direction from the anchor point to
the edge of the hemispherical shell 2. During etching, the etch
rate of the positions close to the anchor point is relatively low,
and the etch rate of the positions close to the edge of the
hemispherical shell 2 is relatively high, which makes sure that
time of etching to the barrier layer is nearly identical in order
to avoid the phenomenon that some regions have been penetrated
before the etching being finished. After etching of the silicon
spherical electrodes, release the thermal oxide layer 8 using
gaseous hydrofluoric acid (vapor HF), so that the hemispherical
shell layer forms the hemispherical shell 2 being hung at the
anchor point, and the hemispherical shell 2 and the several silicon
hemispherical electrodes which surround the hemispherical shell
form several capacitors. Traditional quartz hemispherical gyroscope
utilizes the metal coating method, which leads to small transverse
cross section and low signal coupling coefficient between
electrodes. the electrodes of the hemispherical resonance
micromechanical gyroscope of the present invention utilize
high-doped monocrystalline spherical electrodes with large
transverse cross section and high coupling coefficient between
electrodes, which easily cause noise interference. By adding the
shielded electrodes 7, it could serve to support the hemispherical
shell 2 and minimize the noise interference.
[0055] (5) depositing metal on the surface of the silicon wafer
which is released after the sacrifice of the thermal oxide layer
and make lithography to complete metallization, finally forming the
resonant layer 1 by the process, as shown in FIG. 6. A second
capping layer 11 is vacuum bound on the side of the resonant layer
1 close to the silicon spherical electrodes, so that the
hemispherical shell 2 is absolutely closed in vacuum. The second
capping layer 11 is made of glass material containing through-holes
or silicon material containing through-holes, glass material
containing through-holes or silicon material containing
through-holes guides the silicon spherical electrodes to the
surface of the gyroscope. If the second capping layer 11 is made of
glass material, the anodic silicon oxide-glass bonding method is
utilized. In order to enhance the Q value as much as possible, open
shallow grooves 12 on the surface of the second capping layer 11
which is bound to the resonant layer 1, and a getter film layer 13
is deposited in the shallow grooves 12, then the bonding is
performed. If the second capping layer 11 is made of silicon
material, utilize silicon-silicon direct bonding method, which
doesn't require depositing a getter film layer 13 because it's a
high-temperature bonding with high air tightness. Make lithography
drilling on the second capping layer 11 after bonding, then
sputtering metal electrodes and slicing are performed to finish the
processing.
[0056] As shown in FIG. 7-FIG. 11, the operating principle of the
present invention is as follows: When the hemispherical shell 2
rotates around the central axis as a harmonic oscillator, the
Coriolis effect is generated so that its vibration wave processes
relative to the hemispherical shell 2 in the ring direction. When
the hemispherical shell 2 turns around its central axis at an
angle, the vibration wave turns reversely to the hemispherical
shell 2 at the same angle, and, wherein K is called angular-gain
factor. As long as the angle which the vibration wave turns
relative to the hemispherical shell 2 has been measured, the angle
which the hemispherical shell 2 turns around the central axis could
be measured, then an angular rate could be obtained by
differentiating the rotation angle. So the measure object of the
hemispherical resonance gyroscope is actually the phase of the
resonant mode, which is different from the silicon micromechanical
resonance gyroscope measuring the amplitude as usual. At present
most MEMS gyroscope is on the basis of resonance amplitude
measurement, and its sensitivity depends on the amplitude. However,
the noise signal increases along with the increase of the
amplitude, which restricts improvement of the SNR. The sensitivity
of the hemispherical resonance gyroscope is independent of
amplitude, and its driving voltage could be very low, as a result
its output noise could be significantly reduced. Therefore, the
accuracy of the silicon MEMS hemispherical resonance gyroscope
could be raised one to three orders of magnitude compared with the
MEMS comb gyroscope products in the prior art.
[0057] The resonance mode of the hemispherical shell 2 could be
acquired by finite element analysis. Typical resonance modes have
been shown in FIG. 8-FIG. 11, including four antinodes resonance
mode, three antinodes resonance mode, five antinodes resonance mode
and pendulum resonance mode. The operating resonance mode of the
hemispherical shell 2 mentioned above, i.e. the lowest resonance
mode is the four antinodes mode, the resonance frequency is 2.0-150
kHz, typically 13-20 kHz. The operating stability of a low
resonance mode is usually better than a high order resonance
mode.
[0058] The silicon hemispherical resonance gyroscope of the present
invention is made using isotropic etching process, as well as 3D
spherical lithography and bulk silicon production process. The
diameter of the hemispherical shell 2 is about 2 mm or less, and
the thickness of the hemispherical shell 2 is about 2. Because the
silicon hemispherical resonance gyroscope of the present invention
utilizes MEMS micromachining method, wafer-level packaging could be
achieved, as well as batch production capacity, and the cost could
be significantly reduced, meanwhile advantages of the hemispherical
gyroscope such as high accuracy could be retained. It's possible
that the present invention could bring a revolution to the inertial
technology field, and make the navigation system become universal
and low price in the future.
[0059] In another embodiment, as shown in FIGS. 13-15, the silicon
spherical electrodes including driving electrodes 4, equilibrium
electrodes 5, quadrature correction electrodes 14 and shielded
electrodes 7. There are four shielded electrodes 7 which are
symmetrically distributed along the circumferential direction of
the hemispherical shell 2, and quadrature correction electrodes 14
are tuning electrodes for quadrature correction. The shielded
electrodes 7 converge at a point and the converging point is the
anchor point 2a of the hemispherical shell 2, so that the shielded
electrodes 7 could serve to support the hemispherical shell 2. The
mechanical connection and electrical connection of the shielded
electrodes 7 and the hemispherical shell 2 are accomplished through
the anchor point 2a. The hemispherical shell 2 and several silicon
spherical electrodes which surround the hemispherical shell 2
constitute several capacitors. The hemispherical shell 2 has a
concave inner surface and an outer surface opposite to the inner
surface, and top point of the hemispherical shell being its anchor
point 2a. The radius of the hemispherical shell 2 is 600-5000
.mu.m, which is typically 1200-1800 .mu.m; and the thickness of the
hemispherical shell 2 is 0.5-10 .mu.m, which is typically 2.0-5
.mu.m.
[0060] The object of the embodiments mentioned above is only to
illustrate technical ideas and characteristics of the present
invention, therefore those skilled in the art could understand
contents of the present invention and implement the invention, but
not to limit the scope of the present invention. All the equivalent
alternations or modifications according to the spirit substance of
the present invention should be covered by the scope of the present
invention.
* * * * *